1. Field of the Invention
The present invention relates to a linear guide apparatus and, in particular, to an overrun preventing device of a linear guide apparatus for preventing a slider from falling off of a guide rail.
2. Description of the Relevant Art
With reference to FIG. 16, a prior art linear guide apparatus includes a guide rail 1 which has rolling member rolling grooves 3 extending in an axial direction and formed in both side surfaces 1c. A slider 2 straddling the long guide rail 1 has rolling member rolling grooves (not shown) in inner surfaces of both side walls so that the rolling member rolling grooves of the slider 2 respectively oppose the rolling member rolling grooves of the guide rail 1. A multiplicity of rolling members (balls or rollers) are rollably inserted in the mutually opposing rolling member rolling grooves. When the slider 2 moves on the guide rail 1 in an axial direction, the rolling members circulate through circulating routes provided within the slider 2 while rolling and moving. However, in a condition in which the slider 2 has been removed from the guide rail 1, the rolling members are held in the rolling member rolling grooves by rolling member retainers which are mounted in the slider 2 to prevent the falling off of the rolling members. On the other hand, when the slider 2 is assembled to the guide rail 1, the rolling member retainers are accommodated in retainer relief grooves 3a formed in the bottoms of the rolling member rolling grooves 3 so that the rolling member retainers are not in contact with the guide rail 1 and do not disturb the circulation of the rolling members.
The guide rail 1 is secured by bolts to, for example, a machine tool, a robot, a measurement equipment, a precision positioning table, and the like. On the other hand, for example, in the case of the machine tool, a driven member, such as a cutter, is fixed to the slider 2 by screws and is moved linearly along the guide rail 1 together with the slider 2.
A prior art overrun preventing device of the linear guide apparatus is solely intended to prevent the slider 2 from being separated or removed from the guide rail 1 during transportation of the linear guide apparatus or before the linear guide apparatus is mounted on a machine base at an installation site. Accordingly, for example, as shown in FIG. 16, a rubber plug 6 is inserted into a fixing bolt bore 7 of the guide rail 1.
However, in such a prior art overrun preventing device of the linear guide apparatus, since the rubber plug 6 is removed from the fixing bolt bore 7 of the guide rail 1 at the time of assembling the linear guide apparatus at the installation site, the slider 2 frequently falls off of an end of the guide rail 1 due to overrun of the slider 2 during an accuracy check in operating the linear guide apparatus. Thus, the linear guide apparatus becomes inoperative.
Furthermore, in general, the linear guide apparatus is used in combination with a feed mechanism employing a ball screw and, in this case, since an overrun preventing stopper is provided on the ball screw, an overrun preventing device of the linear guide apparatus is unnecessary. However, when the linear guide apparatus is used in combination with another feed device, for example, a linear feed device, such as a air pressure cylinder, a hydraulic cylinder, a rack and a pinion, or the like, the overrun preventing stopper is never used. Accordingly, the slider 2 sometimes overruns and falls off of the end of the guide rail 1 and is damaged.